(a) Field of the Invention
This invention relates to an improvement in the process for preparing intermediates for the preparation of quinoline antibacterial agents.
(b) Information Disclosure Statement
Ethyl 7-chloro-6-fluoro-1,4-dihydro-4-oxo-3-quinolinecarboxylate is a known compound, described by Koga et al., J. Med. Chem. 23, 1358-1363 (1980). This reference describes the preparation of the compound according to the following flow-sheet: ##STR1##
3-Chloro-4-fluoroaniline (I) and diethyl ethoxymethylenemalonate were heated at 120.degree.-130.degree. C. to give diethyl (3-chloro-4-fluorophenyl)aminomethylenepropanedioate (II). The latter was cyclized by heating it at reflux in diphenyl ether to give the quinoline III.
Koga et al. also describe the N-alkylation of III with potassium carbonate and ethyl iodide in dimethylformamide solution.
Wentland and Bailey U.S. Pat No. 4,499,091, issued Feb. 12, 1985 discloses Compound III as an intermediate for 1-amino-substituted-1,4-dihydro-4-oxo-6-fluoro-7-heterylquinoline-3-carbox ylic acids, useful as antibacterial agents.